Over the first four years of life children develop the skills to interact with both familiar and unfamiliar peers and adults in a socially appropriate manner. They leam to modulate their behavioral and emotional responses across multiple contexts and they develop skills to overcome initial hesitations to engage others. There are, however, instances, in which children are less successful in the development of regulated social behavior. Some childrendisplay social withdrawal and miss out opportunities to interact with peers and develop friendships. The lack of such experiences is often associated with low self-esteem and signs of depression in withdrawn children during the school years. Other children display impulsivityand low frustration tolerance and often find themselves engaged in conflict and struggles with peers and adults. The processes by which infants and young children develop the skills for regulated social interaction involve the interaction of their inborn temperamental styles with supportive, guiding, caregivtngbehaviors across a variety of contexts, and the development of certain information processing skills that facilitate the transition from the use of external supports in the modulation of behavior to internal self-reliant responses. In order to fully understand these processes, we will study each of these components and their interactions over time. The current proposal draws upon the research literature in four domains: temperament, frontal EEC asymmetry, mother-child interaction and socialization and the role of cognitive processes in the development of regulated and unregulated social behavior. We propose a longitudinal study in which will select two temperament groups, infants who are temperamentally fearful and infants who are temperamentally exuberant. We will follow these children over the first four years of life assessing the expression of their temperament, the pattern of maternal caregiving, and the development of executive function skills. We will assess frontal EEG asymmetry in these infants and over time. This measure has been found to be a significant correlate of temperament and our repeated assessment of frontal EEG asymmetry and child temperament will provide an important model for understanding the plasticity of neural development and the coordination of brain behavior relations in early childhood. Our proposed study will attempt an innovativeanalytical approach, growth modeling with latent cluster analysis so that we might identify clusters of children who show particularpatterns of change or continuity in the expression of temperament over time. To accomplish this we will repeatedly assess the child's social behavior with an unfamiliar peer across ths grant period. This program of research will identify the significant components that mediate a child's inborn temperament to produce either socially appropriate and regulated social behavior or socially inappropriate and maladaptive unregulated social behavior.